These labeled compounds are absolutely required for all of our diagnostic work in Gaucher's disease and Niemann-Pick disease respectively. They are alsoo necessary for the detection of heterozygous carriers of these disorders and for the prenatal monitoring of pregnancies at risk for these diseases. These labeled substances are also used for measuring the purification of enzymes for our investigations of enzyme replacement therapy for patients with these disorders. The compounds are also necessary for monitoring the fate and disease and Niemann-Pick disease. In order to perform this research, it is necessary that one gram of glucocerebroside-14C labeled in the D-glucose portion of the molecule and one gram of sphingomyelin-14C labeled in the choline portion of the molecule be provided each year. The specific radioactivity of each of these labeled substances must be at least 1 x 10-6 disintegrations per minute per the designated compounds.